There is a number of reasons that it is not working.
1: Have you download the most recent patch for Jedi knight 2 with you can use this link to do. Jedi Knight Patch 1.04 (
http://support.lucasarts.com/patches/jedioutcast2.htm)
2. If you are trying to play a map that is listed under the Mods section of the server you have to go to the Setup screen and activate the Allow Download option this tells you computer to download the item need to see and play. I mean if someone has a new model or a new map the computer will download those items so that you can see them on your screen and use them later.
See if that works!!!!